Method and anode for electrodeposition of rust-resisting coatings



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to Drawing. Original application fled January 5, 1994, serial No. 684,506. Divided and this applica- To'all whom it mm concern:

Be it known that I, Gmusrmx Jonn WERNLUND, a citizen of the United States, and resident of Tottenville, in the county of 6 Richmond and State of New York, have invented certain new and useful Improvements in Methods and Anodes for Electrodeposition of Rust-Resisting Coatings, of p which the following is a specification.

-This invention relates in general to the electroplating on iron and steel or other metal articles of allo s with'zinc of metals having a higher so ution potential 7 than iron, such as cadmium, this application being a division of my application, Serial No. 684 506 filed January 5, 1924. I

- admium 'has many properties which render it advantageous over other metals and alloys as a protective coating for metals such as iron and steel. It is light in color and has a higher solution potential than iron, thus ten ing to protect the iron from corrosion. As its solution potential is higher than-that of iron and lower than that of zinc, the same weight of protective coating of cadmium affords more protection to atmospheric corrosion than is ofiered by straight zinc.'. Also more cadmium than zinc can be deposited per unit of. current used. The oxide coating formed b'y-atmospheric or other corrosion of cadmium is thinner and more adherent than that formed on zinc, consequently the tendency of 'cadmium toscale ofi and waste away is much lessvplronounced than that of zinc.

ile I have found that ure cadmium coatings can be efiectively epo'sited elec-, trolytically, I have further found that alloy coatingscomp-rising cadmium retain in large pidity of deposit and can be muchvv more cheaply and "conveniently produced. tlxan c5 the alternative methods given in III dependin upon their condition. When measure the advantageous features of pure cadmium coatings in durability and 'ra-' tion filed lull-8,1925. Serial Io. 41,867.

- zinc with less thickness, good color of coatmg, and economy of current. The advantage of using mercu in combination with cadmium or zinc an cadmium is that the resultant coatin is more resistant to corroslon than ca mium or zinc alone. .The cathode (potential is raised with consequent increase throwing power.

Such a coating may be formed by the use of a plating solution to which the proper addltion of cadmium or cadmium and mercury compounds soluble in the bath have been made, or the metals can be furnished to the solutlon by theuse of cadmium anodes andzmc anodes or alloy anodes. If mercury is not desired. in the final product a banary anode of zinc and cadmium can be use Examples of the scope of are as follows: 1

7 Example; I To plate steel casters with a zinc cadmium mercury alloy, they are cleaned b& one of xample this invention a chemically c ean surface has been obtained they'may berpl ated in the following solu- Water 1 L. I .1 gal. 1 Sodium cyanide 46 G. 6 oz. Sodium hydroxide 30 G. 4 Zinc cyanide 1 30 G. 4 Cadmium hydrate 7.5 G. 1 Mercuric ox1de 0.1 G. 0.0125 oz. Otherconditions maintained are as follows Tem erature 40 C.

13. F 3 to 6 volts. f

urrent 25 amperes per sq. t.

Anodes. Zinc.

The bath must be replenished from time to time as the several ingredients become depleted. An average analysis of the coating obtained in zinc 70-80%, cadmium 20-60%, mercury 1-2%.

Y Emmplell.

I-have also found that'the zinc, cadmium and mercury contents of'the bathimay (be stabilized by using'zinc cadmium mere ry alloy anodes to supply the desired qu ntities of these metals to thesolution. A preferred composition-of such an alloy anode 1s Per cent.

- Cadmium 2 Mercury '2 For some purposes,; I have used. a zinc cadmium mercury alloy anode of the following composition: I

- Per cent. Zinc Cadmium 5 Mercury m 2 to give a coating of approximately the same 2. Method of-electrode-positing a rust resistant deposit of zinc, cadmium and mercury which consists in electrodepositing these metals from a solution of their salts in an a ueous sodium cyanide-sodium hydroxide so ution wherein the article receiving the deposit is the cathode and an alloy of zinc, cadmium and mercury isthe anode.

3. In cadmium electro lating from a cyanide bath, the step which consists in depositing cadmium in the presence of zinc and mercury to produce a coating of cadmium alloyed with zinc and a minor percentage of mercury.

In zinc electroplating from a cyanide bath, the step which consists in depositing zinc in the presence of cadmium and mercury to produce a coating of zine alloyed with cadmium and a minor percentage of cercury.

5. In zinc electroplatin from a cyanide bath, the step which consists in depositing zinc in the presence of a salt of cadmium of cadmium and mercury.

6. Method of electrodepositing a cadmium alloy which consists in making the article to be plated the cathode and providing an anode whose'major constituent is zinc the minor constituents being cadmium and mer- 7 The method of electrodepositing an alloy coating of zinc and cadmium which consists in making the article to be lated the cathode and providing an anode w ose major constituent is zinc and whose minor constituents are cadmium and mercury.

8. The method of electrodepositing an al loy coating of zinc cadmium and mercury which consists in making the article to be plated the cathode and providing an anode whose major constituent is zinc and whose minor constituents are about 5% of cadmium and about 2% of mercury.

9. The method of electrodepositing an alloy coating comprising cadmium from 2- 30%, zinc from 7 O97 and mercury from 1-2% which consists in electrodepositing these metals from a solution of their salts in corresponding proportions in an aqueous sodium iyanide-sodium hydroxide solution.

-10.- he methodtof electrodepositing an alloy coating "comprising cadmium from 280%, zinc from -97%, and mercury from 12% which consists in electrodepositing these metals from a solution of their salts derived from a ternary alloy anode of such metals in corresponding proportions in an aqlueous sodium cyanide-sodium hydroxide so ution.

11. An anode for electroplating comprisiriiig zinc cadmium and mercury in amounts e ective for the purposeset forth.

12. An anode for electroplating com rising zinc, between 5 and 30% of cadmium, and about 2% of mercury.

13. An anode for electroplating comprising zinc, c admium and mercury in which the mercuryl is in a smaller percentage than either t e zinc or the cadmium.

Si ed at Perth Amboy, in the county of Mid lesex and State of New Jersey this 29th day of June A. D. 1925.

CHRISTIAN JOHN WERNLUND.

so It 

